It's a big country with large regions that are still comparatively poor and agricultural. The latter two factors are what the EU pays for and the first works as a multiplicator.

Per capita it looks a bit different. According bpd.de the main recipient per capita in 2022 was Estonia with 677 Euros per capita and year and the main contributor is indeed Germany with 237 Euros. Poland "only" gets 279 Euros per person and year.